Well, Autumn hasn’t officially started yet, but here we go! These first few weeks of the Autumn term are interesting ones, the interface between the fading summer and the oncoming crisp golden-ness of October making for some great wildlife-watching opportunities.

Already the days are starting to have that September chill in the air, and soon the numbers of insects will be diminishing. There are several species of butterfly still to be seen ‘on the wing’ into September and October, and in fact these are some of our most colourful and familiar. Today we are highlighting a well-known and popular species, the Small Tortoiseshell.

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THE SMALL TORTOISESHELL

Aglais urticae

One of the most colourful species of butterfly to be seen in Britain, the Small Tortoisheshell is widespread throughout the country. Partly, this is due to the wide availability of its foodplant, the common stinging nettle. However, in recent years it has become significantly less common, with recent studies citing as high as 52% decreases in some areas. There is some speculation that this is because of the spread of a parasitic fly, Sturmia bella, whose eggs are laid on nettle leaves and then ingested by caterpillars. You can read more about a study into this here.

On the bright side, the butterfly seems to have enjoyed a good summer this year, no doubt boosted by our scorching July!

There are two broods of the species each year. Adults hatch in July and August, and can survive not only our Autumn, but winter as well. Although you probablyt won’t see them, they are one of the few species that hibernate, in sheds, outbuildings and eaves of buildings. On warm February days you might be startled to find one of these overwintering specimens flying around your house, having woken prematurely!

The overwintered Tortoiseshells are some of the first butterflies to be seen each year, and breed again in the Spring.

CLASSROOM POTENTIAL

Small Tortoiseshell caterpillars – coming to a classroom near you?

The Small Tortoishell is a great species to use in class supporting life cycles. Caterpillars are easily bred in captivity, and fresh nettles are easy to find to top up their food supply; it’s a great one to rear in your classroom, and the butterflies can be released anywhere. The organisation WorldWideButterflies provides special school rearing packs (as well as lots more) here, which are available from September. Obviously, this sort of project provides lots of great learning opportunities. As well as purely Science objectives, you could work in literacy themes of explanations (the life cycle), instructions (how to care for the caterpillars), as well as poetry, descriptive writing and so forth. As well as learning opportunities, there is the potential to help boost wild stocks of a species not as common as it was.

EXTINCT RELATIVE

Did you know that the Small Tortoiseshell has a much rarer relative?

The Large Tortoiseshell. Picture source: Wikipedia

The Large Tortoisheshell Nymphalis polychloris, is superficially similar, but a paler orange and, you guessed it, larger. It once lived alongside it’s smaller cousin in the U.K., but has been declared extinct here for a number of years. Partly this was due to its more specialised needs; the caterpillars fed on elm trees, much less common than nettles. It hasn’t been seen for certain since the 1950s, although there are hopes for a comeback in the Isle of Wight.